Summary of Work: A low frequency (155, 9/59) of H-ras codon 61 mutations was detected in hepatocellular neoplasms when compared to the higher frequency (59% of this study and 56% of historical data) in spontaneous liver neoplasms. There was no difference in the mutation frequency or spectrum among exposure groups or between benign and malignant heopatocellular neoplasms. K-ras mutations at codons as 12, 13, and 61 and H-ras mutations at codon 117 were not detected in hepatocellular newplasms. The frequency to be similar to those identified in liver neoplasms from the structurally related chemical tetrachloroethylene (TCE). These data suggest that FGE-induced heptocellular neoplasms and newplasms and neoplasms from structurally related chemical classes most likely develop by pathway ndependent of H- and K-ras proto-oncogene activation. The manuscript is in preparation.